An optical transceiver installed within an optical communication system includes an optical module that has a light-emitting device or a light-receiving device coupled with an external optical fiber in the optical communication system. In order to couple the optical device above with the external optical fiber, a coupling portion is prepared in the optical module, and the coupling portion includes, for a light-emitting module, a stub securing a coupling fiber therein and a sleeve. The optical device is optically coupled with the coupling fiber, while, the external fiber with a ferrule in an end thereof also is coupled with the coupling fiber by inserting the ferrule into the sleeve and making the ferrule abut against the coupling fiber. Thus, the external fiber is optically coupled with the optical device.
The optical device, which electrically couples with circuits in the optical transceiver, such as a driver for driving the light-emitting device or a pre-amplifier for amplifying a faint signal converted by the light-receiving device, is necessary to be grounded to, what is called as the signal ground. On the other hand, a housing of the optical transceiver is unavoidably grounded to, what is called as the frame or chassis ground. The latter ground, the frame or chassis ground, is strongly influenced by ambient electrical conditions, in other words, the electro-magnetic interference (EMI). Accordingly, the signal ground is strongly preferable to be isolated from the frame or chassis ground. In the optical module, a cover that secures the sleeve is grounded to the frame or chassis ground, while, a bush that secures the stub is grounded to the signal ground. Accordingly, a mechanism or a structure to isolate the cover from the bush electrically is inevitable in the optical module.